I was wondering if anybody had any experience with slightly porting into the outter oil control ring track and it manifesting in oil consumption/smoking on cold starts? I cut a very aggressive port in my FD housings and have noticed that whenever the block cools after running at full temperature I smoke pretty heavily for about 5 seconds. It almost seems that after cooling/cinching up from heat expansion oil is being drawn onto some of the combustion faces.





To clarify, I dont have any oil consumption issues while hot or boosting, only on a cold or semi cold start. Your suggestions would be great, thanks!

 

In the olden days, it was not all that uncommon to find people who would eliberately port into the outer track, just to make the port bigger. In racing is does the same thing yours does, but in spades. But with the idle up around 2,000 to 2,200 RPM the smoking is less obvious. Once at speed it is not noticable at all. It would be a disaster on the street. This practice was limited to those folks in E Production, where a bridgeport was not allowed. So in some cases you would see 6 port irons converted to 4 port and then ported into the track, and finger ports were back as well. The last time I looked at the rule book, Dave Lemon Mazda Trix)had helped the SCCA write some rules about moving the open line to prevent porting well beyond the track of the leading end of the side seal. In fact you just leave enough material to keep the corner seal from falling into the port. You replace the side seals every week,and the ends look like skis but the power is there for a while.



But all of this has to do with NA engines, where there is less than one Bar of pressure in the intake runner. So the very micro amount of oil lost on each revolution is not a problem in a racer.



In the street car you would wonder how long the reactor would last with oil carboning up the works. Then there is the boosted runner, where the space between the oil scrapers is being pressurized on each revolution. On the one hand, the pressure might help the inner ring work a bit better, and you have the pressure helping your situation by reducing oil consumption, and lowering smoking once under way. On the other hand, it is likely that the appearent lack of oil consumption is a result of added fuel dilution of the oil. All rotaries do this to a smaller extent. More when used hard, and a lot when raced. There is a use of sharper edged scrapers, (racing part)and double springing the inner scraper to reduce this problem. To what extent this would affect the boosted engine is speculation.



If the smoking is only 5 seconds, it sounds as though it is a minimal situation. I would change the oil often and use a racing oil for the higher zinc content. Of course this is all just a guess.



Lynn E. Hanover